This invention relates to a correcting method of a difference between dot formation positions in a reciprocally operation of a liquid ejecting head such as a record head used with an image record apparatus such as a printer, a color material ejection head used for manufacturing a color filter of a liquid crystal display, etc., an electrode material ejection head used for electrode formation of an organic EL display, an FED (surface light emission display), etc., or a biological organic substance ejection head used for manufacturing a biochip, a general liquid ejecting apparatus using the liquid ejecting head, a computer program, a computer system, and a correction pattern.
Some ink jet printers wherein a print head ejects ink for printing while the print head scans in a main scanning direction have a function of “two-way print” for ejecting ink in a go way and ejecting ink in a return way for printing.
To perform two-way print in such a printer, correction needs to be made so that dot formation positions of ink droplets ejected in the go way and the return way in the main scanning direction (namely, hit positions of the ink droplets on print paper) match.
As a method of determining the correction amount of a dot formation position, a method disclosed, for example, in JP-A-7-32654 (abstract) is available. Determining the correction amount in a color printer based on such a method will be discussed with reference to FIG. 22. First, in the go way, a plurality of longitudinal lines extending in a subscanning direction (500a to 500h) are printed with a given spacing in the main scanning direction using a nozzle at the tip of a print head. Next, likewise a plurality of longitudinal lines (501a to 501h) are also printed in the return way. In the return way, a different correction amount is added to the spacing between the longitudinal lines in the go way for printing the longitudinal lines with a little different spacing. In the example in FIG. 22, the difference between the longitudinal lines 500a and 501a is ΔL1 and the difference between the longitudinal lines 500b and 501b is ΔL2. ΔL1 and ΔL2 have the relation of ΔL1>ΔL2.
The user, etc., selects the point where the longitudinal lines 500a to 500h printed in the go way and the longitudinal lines 501a to 501h printed in the return way are printed most linearly, and the correction amount added when the selected longitudinal line was printed is determined to be the correction amount in performing two-way print. In the example in FIG. 22, the longitudinal lines 500d and 501d are printed most linearly and therefore the correction amount added when the longitudinal lines were drawn is determined to be the correction amount in performing two-way print.
By the way, to print the print correction pattern as shown in FIG. 22, after the longitudinal lines 500a to 500h are printed in the go way, the print head is moved to the home position (the right end in FIG. 22), a predetermined correction amount is set, and the longitudinal line 501h is printed. After the print head is again returned to the home position, a correction amount different from the preceding correction amount is set and the longitudinal line 501g is printed. As similar operation is repeated, the longitudinal lines 501f to 501a are printed and printing the print correction pattern is complete.
Therefore, to draw the longitudinal lines 501a to 501h in the return way, it becomes necessary to repeat the operation of returning to the home position and setting the correction amount each time one longitudinal line is drawn, and thus there is a problem of taking time in drawing the print correction pattern.
In recent years, to improve the resolution of an image, there has been a trend to decrease the amount of an ink droplet ejected from a print head. For example, in a color printer, etc., it is being common practice that the amount of an ink droplet is about several picoliters.
Therefore, to use an ink droplet of such a minute amount to draw a longitudinal line as shown in FIG. 22, the line width is very narrow and thus the visibility is degraded and an erroneous determination may be made; this is a problem.
To print a natural image (for example, an image picked up by a numeralal camera) in an ink jet printer, seven color inks (for example, pale color inks, namely, light cyan ink and light magenta ink and dark yellow ink in addition to cyan, magenta, yellow, and black inks required at the minimum for color print) may be used. On the other hand, to execute color print of an illustration, etc., requiring only limited colors, four color inks of cyan, magenta, yellow, and black are used and thus light cyan, light magenta, and dark yellow inks are not used. Thus, in recent years, there has been provided an ink jet printer of the type wherein different color inks are provided as separate cartridges and seven print heads to and from which the corresponding ink cartridge can be attached and detached are included. To print a natural image, the seven color ink cartridges are used and to increase the print speed or to print an illustration, cyan, magenta, and yellow ink cartridges can be mounted replacing the light cyan, light magenta, and dark yellow inks for using two print heads for each color to print.
However, to use four color inks to print, the ink cartridges of the same color are mounted on two print heads and thus the dot formation positions of ink droplets ejected in the go way and the return way in the main scanning direction must be corrected for different nozzles for ejecting ink of the same color. On the other hand, to use seven color inks to print, it is desirable that the dot formation positions of ink droplets ejected in the go way and the return way in the main scanning direction should be corrected for the nozzles for ejecting light color inks, particularly the nozzle for ejecting light cyan ink and the nozzle for ejecting light magenta ink.
Thus, as the correction values for correcting the dot formation positions of ink droplets ejected in the go way and the return way in the main scanning direction, those for seven-color print and those for four-color print must be set separately. That is, two print correction patterns for determining the correction values for seven-color print and for four-color print must be printed using different nozzles and thus there is a problem of taking time in printing.